Link to the URL

Double brackets around the URL create a link to the URL.

When you type:

This website http://www.backlog.jp/ is useful to solve this bug.
This website [[Backlog>http://www.backlog.jp/]] is useful to solve this bug.
This website [[Backlog:http://www.backlog.jp/]] is useful to solve this bug.

It will appear as:

This website http://www.backlog.jp/ is useful to solve this bug.
This website Backlog is useful to solve this bug.
This website Backlog is useful to solve this bug.